Global Navigation Satellite Systems (GNSS) are satellite systems that can include the United States' Global Positioning System (GPS), Russia's GLONASS, and the European Union's GALILEO. Such systems are used primarily in navigation applications, for example, to determine receiver positioning. GPS has been in operation since 1978 (globally since 1994) and was initially developed to provide precise positioning for military purposes. Today, GNSS systems are used for many civilian and military applications including navigation, surveying, time referencing, geo-fencing, weather data, self-driving cars, etc.
As the GNSS electromagnetic signals traverse the intervening distances from satellites in orbit to various receivers, the signals can be refracted due to the negatively charged ionosphere, moisture in the atmosphere, and the mass of the dry atmosphere. Such refraction can create errors in positional accuracy of GPS trilateration. Previous GNSS stations utilize mapping functions to determine the appropriate dry atmosphere delay for signals arriving at different angles above the horizon. These mapping functions generally use an estimate, such as surface pressure, to calculate the amount of mass traversed for any angle. In addition, the error introduced by the ionosphere can be relatively large when the satellite is near the observer's horizon, when the vernal equinox is near, and/or when sunspot activity is severe. Error can also be introduced by non-uniform moisture content in the atmosphere. The corresponding positional errors can vary as a function of weather, magnetic activity, location, time of day, direction of observation, temperature, atmospheric pressure, etc.
A need exists for improved systems and methods to address such challenges.